Erwinia

Erwinia is a genus of Enterobacteriaceae bacteria containing mostly plant pathogenic species which was named for the famous phytobacteriologist, Erwin Frink Smith. It contains gram negative bacteria related to Escherichia coli, Shigella, Salmonella and Yersinia. They are primarily rod-shaped bacteria.

Many infect woody plants. A well-known member of this genus is the species E. amylovora, which causes fire blight on apples, pears, and other Rosaceae crops; E. tracheiphila on the other hand causes bacterial wilt of cucurbits. Other familiar species, such as E. carotovora (another major cause of plant diseases), are more distantly related to the fire blight bacterium, and been moved to genera Brenneria, Dickeya and Pectobacterium.^[1] Two-dimensional polyacrylamide gel electrophoresis of the secreted proteins of Erwinia carotovora subsp. atroseptica revealed alow-abundance protein that was identified by mass spectrometry as a homologue of a Xanthomonas campestris avirulence protein with unknown function. The predicted Svx protein has an N-terminal signal sequence and zinc binding-region signature, and the mature protein is post-translationally modified. A 2D difference gel electrophoresis (DIGE) showed that the protein is secreted by the type II (out) secretion apparatus, which is also responsible for the secretion of the major known virulence factors, PelC and CelV. Transcription of the svx gene is under Nacyl- homoserine lactone-mediated quorum-sensing control. The svx gene was inactivated by transposon insertion. The mutant showed a decrease in virulence in potato plant assays, demonstrating a role for Svx in the pathogenicity of E. carotovora subsp. atroseptica. These results show that Svx is a previously unidentified virulence determinant which is secreted by the out machinery and is regulated by quorum sensing, two systems employed by several other virulence factors. Thus, the type II secretory machine is a conduit for virulence factors other than the main pectinnases and cellulase in E. carotovora subsp. atroseptica.^[2]

Species

Species remaining in Erwinia are:

• Erwinia amylovora
• Erwinia aphidicola
• Erwinia billingiae
• Erwinia mallotivora
• Erwinia papayae
• Erwinia persicina
• Erwinia psidii
• Erwinia pyrifoliae
• Erwinia rhapontici
• Erwinia toletana
• Erwinia tracheiphila
• Candidatus Erwinia dacicola

References